The deposition by molecular beam dosing of halogen molecules on rare-gas surfaces has been studied with molecular dynamics simulation. Specifically we have considered films formed by the sequential adsorption reactions : X(2g)+X(2)[Theta](ads)-Rg(111)[T]-->X(2(ads))-X(2)[Theta](ads)-Rg(111)[T], where Theta is the film coverage defined by X(2)[adsorbed]/Rg[surface], T indicates the substrate temperature, X(2) is the halogen adsorbate which is either chlorine or bromine, and Rg indicates the rare-gas substrate which is either argon or xenon. The structure of halogen adlayers was studied as a function of coverage for films grown on rare-gas substrates at different temperatures. Chlorine and bromine films on argon exhibit orientational ordering and islanding with increasing coverage. The tendency of the halogen diatoms to align along the surface normal with increasing coverage is strongly enhanced by higher temperatures in the case of chlorine on xenon, moderately enhanced in the case of chlorine on argon, and unchanged in the case of bromine on argon. Chlorine and bromine films form three-dimensional aggregated structures on argon at 15 and 25 K. Chlorine forms a two-dimensional amorphous layer on xenon at 15 K and a highly ordered layer at 50 K. The dynamics of the molecular adsorption event were studied at three different coverages : Theta=0.05, 0.25, and 0.5. At all these coverages, we observed finite possibility of diffusional motion of adsorbate on the surface immediately after it lands : This was not seen at zero coverage.